Question

我是Xamarin Forms和XAML的新手，我想填写<ListView>约会。我的XAML看起来像这样：

<ListView x:Name="appointmentsView"
          ItemsSource="{Binding appointmentList}" 
          Grid.Row="1"
          AbsoluteLayout.LayoutBounds="0.50, 0.2, 1, 0.5"
          AbsoluteLayout.LayoutFlags="All">
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell> 
                <ViewCell.View>
                    <Label TextColor="Black" Text="{Binding app1}"></Label>
                </ViewCell.View>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

代码如下：

public partial class Home : ContentPage
{
    public ObservableCollection<Appointment> appointmentList = new ObservableCollection<Appointment> ();

    public Employee Tom { get; set; }
    public Appointment app1 { get; set; }

    public Home ()
    {
        InitializeComponent ();

        Tom = new Employee("Tom", "Tommen");
        app1 = new Appointment(new DateTime(), Tom);

        appointmentList.Add(app1);
        appointmentsView.ItemsSource = appointmentList;
    }

当我调试应用程序时，列表中没有任何内容，如果有人能告诉我我做错了什么，我真的很感激！

Answer 1

这实际上取决于Employee和Appointment的定义方式。例如：

public class Appointment
{
    public DateTime AppointmentDateTime { get; set; }
    public Employee AppointmentEmployee { get; set; }

    public Appointment(DateTime AppointmentDateTime, Employee AppointmentEmployee)
    {
        this.AppointmentDateTime = AppointmentDateTime;
        this.AppointmentEmployee = AppointmentEmployee;
    }
}

public class Employee
{
    public string FirstName { get; set; }
    public string LastName { get; set; }

    public Employee(string FirstName, string LastName)
    {
        this.FirstName = FirstName;
        this.LastName = LastName;
    }

    override public string ToString()
    {
        return string.Format("{0}, {1}", LastName, FirstName);
    }
}

然后你的XAML应该是：

<ListView x:Name="appointmentsView"
      ItemsSource="{Binding appointmentList}" 
      Grid.Row="1">
        <ListView.ItemTemplate>
        <DataTemplate>
                <Label Text="{Binding AppointmentEmployee}"></Label>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

Answer 2

我不认为listview控件可以像你想要的那样显示复杂的对象（虽然不是100％肯定）。像这样：

public partial class Home : ContentPage
{
    public ObservableCollection<Appointment> appointmentList;

    public Home ()
    {
        InitializeComponent ();

        appointmentList = new ObservableCollection<Appointment>()
        {
            new Appointment { Name = "Tom Tommen", AppointmentDate = DateTime.Now }
        };

        appointmentsView.ItemsSource = appointmentList;
    }
}

public class Appointment
{
    public string Name { get; set; }
    public DateTime AppointmentDate { get; set; }
}

Answer 3

就像提到的@jstreet一样，它可能与您Label绑定到ItemSource中单个项目的方式有关。 Label的{{1}}属性应绑定到单个Text内的属性。在上面的代码中，您尝试将Appointment的{{1}}属性绑定到与{{1}内的Label实例无关的变量} {＆＃39; s Text。

因此，如果Appointment具有ListView属性，并且您希望在ItemsSource中显示每个Appointment的{{1}}，那么您就可以{ {1}}和Name进入：

Name

或者，如果您想将Appointment的{{1}}属性绑定到特定appointmentList ListView内的属性（例如假设Label对象具有名为<ListView ItemSource={Binding appointmentList}> <ListView.ItemTemplate> <DataTemplate> <ViewCell> <ViewCell.View> <Label TextColor="Black" Text="{Binding Name}"/> </ViewCell.View> </ViewCell> </DataTemplate> </ListView.ItemTemplate> </ListView>的属性且Labels对象具有名为{{1}的属性，Text＆＃39; s Appointment }），你的标签将成为：

Answer 4

从Xaml绑定某些内容时，它应位于页面的BindingContext内。多数人称之为 MVVM 和 Binding 的事情可以解决这个问题。

样本型号：

课程预约 { 公共员工员工{get; set;} public string Place {get; set;} public DateTime time {get; set;} }

示例ViewModel：

公共类TestPageVM：INotifyPropertyChanged { #region INotifyPropertyChanged界面公共事件PropertyChangedEventHandler PropertyChanged;

protected void OnPropertyChanged(string propertyName)
{
    var handler = PropertyChanged;
    if (handler != null)
        handler(this, new PropertyChangedEventArgs(propertyName));
}

#endregion

private ObservableCollection<Appointment> appointmentList;
public ObservableCollection<Appointment> AppoitmentList
 {
    get{return appointmentList;}
    set
    {
        appointmentList = value;
        OnPropertyChanged("AppoitmentList");
    }
 }
 //ctor

 public TestPageVM()
 {
    appointmentList = new ObservableCollection<Appointment>();
    AppoitmentList.Add(new Appointment(){
        Employee = new Employee("Johm Doe"),
        Place = "Houston",
        DateTime = DateTime.Now
    });
 }

}

示例视图类初始化：

public partial class主页：ContentPage { 公共之家（） { InitializeComponent（）; this.BindingContext = new TestPageVM（）; } }

-Xaml用法：

<ListView x:Name="appointmentsView"
          ItemsSource="{Binding AppoitmentList}" 
          Grid.Row="1"
          AbsoluteLayout.LayoutBounds="0.50, 0.2, 1, 0.5"
          AbsoluteLayout.LayoutFlags="All">
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell> 
                <ViewCell.View>
                    <Label TextColor="Black" Text="{Binding Employee.Name}"/>
                    <!--can also show place of appointment like: <Label TextColor="Black" Text="{Binding Place}"/> -->
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

为什么我的列表视图似乎是空的？

4 个答案: